CN106317273B - Ultra-high molecular weight ultrafine polyethylene powder and preparation method thereof - Google Patents

Abstract

The present invention relates to a kind of super high molecular weight ultra-fine grain diameter polyethylene powder and preparation method thereof, the viscosity average molecular weigh (Mv) of the polyethylene is greater than 1 × 10⁶, the polyethylene powder is spherical or spherical particle, and average grain diameter is 10 μm -100 μm, and standard deviation is 2 μm -15 μm, and heap density is 0.1g/mL-0.3g/mL.Simple, easily controllable, the repeated height of the method step, may be implemented to industrialize.Powder of the invention has both super high molecular weight and ultra-fine particle size range simultaneously, particularly suitable for processed and applied, and is easily achieved graft modification, greatly extends the application field and the scope of application of ultra-high molecular weight polyethylene object.

Description

Ultra-high molecular weight ultrafine polyethylene powder and preparation method thereof

technical field

The invention belongs to the field of polyolefin polymer materials, and in particular relates to an ultra-high molecular weight and ultra-fine particle size polyethylene powder and a preparation method thereof.

Background technique

Ultra-high molecular weight polyethylene (UHMWPE) is a thermoplastic engineering product with an average molecular weight of more than 1.5 million and a linear structure of molecules formed by low-pressure polymerization of ethylene and butadiene monomers under the action of Ziegler catalysts. plastic. The extremely high molecular weight of UHMWPE (the molecular weight of high-density polyethylene HDPE is usually only 20,000 to 300,000) endows it with excellent performance, so that UHMWPE has unique properties that ordinary HDPE and other engineering plastics do not have, such as excellent impact resistance. , wear resistance, chemical corrosion resistance, low temperature resistance, stress cracking resistance, anti-adhesion and self-lubricity, etc., are known as "amazing plastics". The material has excellent comprehensive properties, low density, low friction coefficient, wear resistance, low temperature resistance, corrosion resistance, self-lubrication, and impact resistance, which are the highest among all plastics. Carbon steel and other materials can work under -169℃～+80℃ for a long time, and the physical and mechanical properties far exceed ordinary polyethylene. Can be widely used in metallurgy, electric power, petroleum, textile, paper, food, chemical, machinery, electrical and other industries.

Although UHMWPE as a thermoplastic engineering plastic has excellent comprehensive properties in solid state, its melt characteristics are completely different from general thermoplastics such as ordinary polyethylene, mainly in the following aspects: 1) high melt viscosity; 2) The friction coefficient is small; 3) The critical shear rate is low; 4) The molding temperature range is narrow, and it is easy to oxidize and degrade. Although the processing technology of UHMWPE has developed from the initial pressing-sintering molding to extrusion, blow molding and injection, solution spinning molding and other molding methods after decades of development, due to the above problems of UHMWPE, the processing method Difficulties are brought about, resulting in performance degradation when applied to profiles, films, fibers, filter materials, and the like.

For example, with the increase of UHMWPE content, the viscosity of the system also increases greatly, and the traditional wet process is difficult to handle the high-viscosity stock solution, which limits the application of UHMWPE. For example, in the conventional wet preparation process, polyolefin is first heated and dissolved in paraffin or other solvents to form a homogeneous solution, compressed into thin sheets by a vulcanizer, cooled down, liquid-liquid phase separation occurs, and then extracted-stretched Or stretch-extraction to obtain a porous membrane. Polyolefin will crystallize during the cooling process, resulting in liquid-liquid separation, which makes it difficult for the film to be drawn at a high rate and limits the improvement of the overall performance of the diaphragm. Therefore, it is difficult to use the solution containing ultra-high molecular weight polyethylene to prepare the membrane in the traditional wet process. This is mainly because the liquid-solid phase separation or liquid-liquid phase separation of the homogeneous solution occurs during the cooling process, and the polyolefin will be separated during the phase separation process. Crystallization makes it difficult for the film to be drawn at a high rate, which limits the improvement of the overall performance of the diaphragm.

Therefore, the current research mainly focuses on how to prepare UHMWPE with excellent processing properties. Some researchers have conducted extensive research on the catalysts used in the preparation of UHMWPE, hoping to make breakthroughs in the preparation of UHMWPE with high performance. The catalysts used in the preparation of UHMWPE are mainly metallocene catalysts and Ziegler-Natta catalysts. However, metallocene catalysts are extremely sensitive to temperature. When Cp ₂ ZrCl ₂ is used to catalyze the polymerization of ethylene, the molecular weight of the polymer decreases from 600,000 to 120,000 when the temperature rises from 20°C to 70°C. At the same time, if metallocene catalysts want to achieve high enough catalytic activity, a large amount of expensive methylaluminoxane (MAO) is needed as a co-catalyst, thereby increasing the cost of product preparation; on the other hand, the co-catalyst MAO is not a single-component compound , the production process is likely to cause unstable product performance. Ziegler-Natta catalysts are industrial catalysts for the preparation of UHMWPE. For example, Zhang H.X. et al. [Polym. Bull., 2011, 66, 627] reported the use of Ziegler-Natta catalysts containing internal electron donors to prepare UHMWPE. method, however, the internal electron donor in this Ziegler-Natta catalyst reduces the activity of the catalyst.

Therefore, there is an urgent need for a new preparation method of UHMWPE, which can prepare UHMWPE with excellent performance and ensure that its performance will not be reduced when it is processed into profiles, films, fibers or filter materials, and has better performance. processing performance and wider application prospects.

SUMMARY OF THE INVENTION

One of the objectives of the present invention is to provide a preparation method of ultra-high molecular weight and ultra-fine particle size polyethylene powder.

Another object of the present invention is to provide a powder prepared by the above method, the powder has excellent processability.

In order to achieve the above object, the present invention provides a preparation method of ultra-high molecular weight ultra-fine particle size polyethylene powder, which comprises the following steps:

Under the action of the catalyst, ethylene undergoes a polymerization reaction; wherein, the temperature of the polymerization reaction is -20 to 100°C; in the ethylene, the carbon monoxide content is less than 5 ppm, the carbon dioxide content is less than 15 ppm, and the conjugated diene content is less than 10 ppm;

The catalyst is prepared by a method comprising the following steps:

(a) mixing magnesium halide, alcohol compound, auxiliary agent, part of internal electron donor and solvent to prepare mixture I;

(b) adding the above-mentioned mixture I to the reactor, preheating to -30°C to 30°C, and adding the titanium compound dropwise; or, adding the titanium compound to the reactor, preheating to -30°C to 30°C, adding dropwise Mixture I above;

(c) after the dropwise addition is completed, the reaction system is heated to 90°C to 130°C after 0.5 to 3 hours, and the remaining internal electron donor is added to continue the reaction;

(d) filter out the liquid of the reaction system, add the remaining titanium compound, and continue the reaction;

(e) after completion of the reaction, aftertreatment obtains the described catalyst;

The viscosity-average molecular weight (Mv) of the obtained polyethylene powder is greater than 1×10 ⁶ , and the polyethylene powder is spherical or quasi-spherical particles, with an average particle size of 10-100 μm and a standard deviation of 2 μm-15 μm. The density is 0.1g/mL～0.3g/mL.

According to the present invention, the particle size distribution of the polyethylene powder is approximately normal distribution.

According to the present invention, the temperature of the polymerization reaction is preferably 30-80°C, more preferably 50-80°C.

The present invention also provides ultra-high molecular weight and ultra-fine particle size polyethylene powder prepared by the above preparation method, wherein the viscosity average molecular weight (Mv) of the polyethylene powder is greater than 1×10 ⁶ , and the polyethylene powder is spherical Or quasi-spherical particles, with an average particle size of 10 to 100 μm, a standard deviation of 2 μm to 15 μm, and a bulk density of 0.1 g/mL to 0.3/mL. The powder of the present invention has excellent processability.

According to the present invention, the particle size distribution of the polyethylene powder is approximately normal distribution.

According to the present invention, the viscosity average molecular weight (Mv) of the polyethylene is greater than or equal to 1.5×10 ⁶ , preferably 1.5×10 ⁶ to 4.0×10 ⁶ ; the molecular weight distribution Mw/Mn of the polyethylene is 2 to 15, Preferably it is 2-10.

According to the present invention, the average particle size of the polyethylene powder is preferably 20μm-80μm, more preferably 50μm-80μm; the standard deviation is preferably 5μm-15μm, more preferably 6μm-12μm, still more preferably 8μm-10μm ; The bulk density of the polyethylene powder is preferably 0.15g/mL-0.25g/mL.

Beneficial effects of the present invention:

The present invention proposes a brand-new method for preparing ultra-high molecular weight and ultra-fine particle size polyethylene powder. In the method, by controlling the polymerization temperature of ethylene, the purity of monomer ethylene and adjusting the preparation steps of catalyst, a The ultra-high molecular weight and ultra-fine particle size polyethylene powder has simple steps, easy control and high repeatability, and can be industrialized.

In the present invention, a polyethylene powder with both ultra-high molecular weight and ultra-fine particle size range is synthesized for the first time. It is found through research that the polyethylene powder with the above characteristics is particularly suitable for processing and application, and it is easy to realize graft modification. , which greatly expands the application field and scope of ultra-high molecular weight polyethylene. At the same time, the polyethylene powder also has the following excellent properties: firstly, the wear resistance is very excellent, which is several times higher than the wear resistance index of ordinary carbon steel and copper and other metals; secondly, due to the ultra-high molecular weight, the molecular chain Ultra-long, high impact strength of the material; Thirdly, the chemical resistance of the polyethylene powder is stronger than that of the general polyolefin; Maintains good toughness and strength.

Therefore, the polyethylene powder prepared by the method of the present invention has excellent processing performance, and it is expected to not only save energy consumption in the later forming, film forming, and fiber forming processes, but also can speed up the technological process and prepare higher performance. Material.

Description of drawings:

Figure 1 is a scanning electron microscope image of polyethylene particles.

Detailed ways

[Preparation method of catalyst]

The catalyst used in the preparation method of the present invention can be prepared by the method disclosed in the invention patent application (application number 201510271254.1) submitted by the applicant, the entire contents of which are incorporated into this application by reference.

Specifically, the catalyst used in the preparation method of the present invention is prepared by a method comprising the following steps:

(a) mixing magnesium halide, alcohol compound, auxiliary agent, part of internal electron donor and solvent to prepare mixture I;

(b) adding the above-mentioned mixture I to the reactor, preheating to -30°C to 30°C, and adding the titanium compound dropwise; or, adding the titanium compound to the reactor, preheating to -30°C to 30°C, adding dropwise Mixture I above;

(c) after the dropwise addition is completed, the reaction system is heated to 90°C to 130°C after 30 minutes to 3 hours, and the remaining internal electron donors are added to continue the reaction;

(d) filter out the liquid of the reaction system, add the remaining titanium compound, and continue the reaction;

(e) After the reaction is completed, the catalyst is obtained by post-treatment.

According to the present invention, the step (b) is replaced by the following step (b'):

(b') configuration comprising Mixture II of nanoparticles, dispersant and solvent;

Add the above-mentioned mixture I and mixture II to the reactor to obtain a mixture of the two, preheat to -30°C to 30°C, and add the titanium compound dropwise; or,

The titanium compound was added to the reactor, preheated to -30°C to 30°C, and the mixture of the above-mentioned mixture I and mixture II was added dropwise.

In the present invention, the mixture I is preferably prepared according to the following method: mixing magnesium halide and an alcohol compound in an organic solvent, heating up and keeping the temperature, adding an auxiliary agent and a part of the internal electron donor, and reacting at a certain temperature to obtain Stable and homogeneous mixture I.

The alcohol compound is selected from one or more of C ₁ -C ₁₅ aliphatic alcohol compounds, C ₃ -C ₁₅ cycloalkanol compounds and C ₆ -C ₁₅ aromatic alcohol compounds, preferably Methanol, ethanol, ethylene glycol, n-propanol, isopropanol, 1,3-propanediol, butanol, isobutanol, hexanol, heptanol, n-octanol, isooctanol, nonanol, decanol, sorbitol One or more of alcohol, cyclohexanol and benzyl alcohol, more preferably ethanol, butanol, hexanol and isooctanol.

The internal electron donor is at least one of monoester, diester, monoether and diether compounds, more preferably selected from diester or diether.

The solvent is selected from at least one of straight chain alkanes of 5-20 carbons, branched alkanes of 5-20 carbons, aromatic hydrocarbons of 6-20 carbons or their halogenated hydrocarbons, preferably toluene, chlorobenzene , at least one of dichlorobenzene or decane.

In the present invention, magnesium halide has a carrier role in the preparation of catalysts that can directly obtain sub-micron polyolefin particles, and is one of the components of traditional Ziegler-Natta catalysts, which can make the prepared catalysts have suitable shapes, At the same time, the carrier can disperse the active components on the surface of the carrier to obtain a higher specific surface area and improve the catalytic efficiency of the active components per unit mass. In addition, the function of the alcohol compound is to dissolve magnesium halide as a carrier. In the preparation process of mixture I, the temperature at which the mixed solution is obtained is preferably 110°C to 130°C, more preferably 130°C, and the holding time is preferably 1 to 3 hours, more preferably 2 to 3 hours, and the The reaction time after adding an auxiliary agent or the like is 0.5 to 2 hours, more preferably 1 hour. Therefore, the magnesium halide is dissolved by the alcohol compound at high temperature, and the mixture I is obtained.

According to the present invention, the mixture II is preferably prepared according to the following method: adding nanoparticles, a dispersant and a solvent into a reaction vessel, and ultrasonically treating to obtain a homogeneous mixture II. The nanoparticles are preferably at least one of nano-silicon dioxide, nano-titanium dioxide, nano-zirconium dioxide, nano-nickel oxide, nano-magnesium chloride or nano-carbon balls, more preferably nano-silicon dioxide and nano-titanium dioxide. The particle size of the nanoparticles is preferably 1 to 80 nm, more preferably 10 to 50 nm. Preferably, the added mass of nanoparticles is 0% to 200% relative to the added mass of magnesium halide, more preferably 0% to 20%. The time of sonication is preferably 2 hours. In the present invention, nanoparticles are introduced as seeds for the purpose of accelerating the formation of the carrier and reducing the particle size of the catalyst particles; dispersants and solvents, including ultrasonic treatment, are used to help the nanoparticles disperse, so that each nanoparticles can be Play the role of seed crystals.

According to the present invention, in the mixture II of the step (b'), the nanoparticles are selected from at least one of nano-silicon dioxide, nano-titanium dioxide, nano-zirconium dioxide, nano-nickel oxide, nano-magnesium chloride or nano-carbon balls .

Preferably, the particle size of the nanoparticles is 1-80 nanometers, preferably 2-60 nanometers, more preferably 3-50 nanometers.

The added mass of the nanoparticles is greater than 0% to less than or equal to 200% relative to the added mass of the magnesium halide, and preferably, the added amount of the nanoparticles ranges from greater than 0% to less than or equal to 20%.

In the present invention, in the mixture II of the step (b'), the solvent is selected from linear alkanes with 5-20 carbons, branched alkanes with 5-20 carbons, aromatic hydrocarbons with 6-20 carbons or at least one of their halogenated hydrocarbons.

The dispersant is selected from titanium tetrachloride, silicon tetrachloride or a mixture of the two.

In step (a), the mixing is carried out under heating and stirring to obtain a uniform and stable transparent mixture I.

In step (b'), ultrasonic dispersion treatment is carried out during disposition.

In step (b) or (b'), the dropwise addition is slow dropwise addition.

In step (b) or (b'), the preferred reaction preheating temperature is -20°C to 30°C, more preferably -20°C to 20°C.

The reaction time of step (c) is 1-5 hours, preferably 2-3 hours.

The time for the continued reaction in step (d) is 1 to 5 hours, preferably 2 to 3 hours.

The post-treatment in step (e) may be to wash the obtained product with hexane, and then to dry; wherein, the number of times of washing may be 1 to 10 times, preferably 3 to 6 times.

In step (a), the magnesium halide is selected from at least one of magnesium chloride, magnesium bromide or magnesium iodide.

In step (a), the auxiliary agent may be a titanate compound.

In step (b) or (b'), the general formula of the titanium compound is shown in formula I:

Ti(R) _n X _(4-n)

Formula I

wherein, R is a C ₁ -C ₁₂ branched or straight-chain alkyl group, X is a halogen, and n is 0, 1, 2 or 3.

In step (d), preferably, the reaction system is heated to 90°C to 130°C over 40 minutes to 3 hours, and more preferably the reaction system is heated to 100°C to 120°C over 40 minutes to 2 hours.

It can be seen from the above scheme that the preparation method of the Ziegler-Natta catalyst involved in the present invention is simple in process and easy to industrialize production. In addition, the Ziegler-Natta catalyst prepared by the present invention can produce particles with an average particle size of 10-100 μm, high sphericity, narrow particle size distribution and low bulk density (0.1-0.3/mL) during ethylene polymerization. polyethylene pellets. Through research, it is found that the polyethylene particles obtained by the catalyst prepared by the invention for ethylene polymerization have 20-30 times lower particle size compared with other polyethylenes, the particle size distribution is obviously narrowed and the bulk density can be as low as 0.1g/mL.

[Preparation method of polyethylene powder]

As mentioned above, the present invention provides a kind of preparation method of ultra-high molecular weight and ultra-fine particle size polyethylene powder, which comprises the following steps:

Under the action of a catalyst, ethylene undergoes a polymerization reaction; wherein, the temperature of the polymerization reaction is -20 to 100°C; in the ethylene, the carbon monoxide content is less than 5 ppm, the carbon dioxide content is less than 15 ppm, and the conjugated diene content is less than 10 ppm;

The catalyst is prepared by the above-mentioned preparation method of the catalyst.

It is found through research in the present invention that simply controlling the preparation method of the catalyst can indeed well control the particle size of the powder, but the molecular weight of the prepared polyethylene is not high. The molecular weight of the polymer, the inventor has made many attempts, and found that it is a simple and effective method to control the temperature of the polymerization reaction and the purity of the monomer, and it will not affect the effective particle size of the polymer. Control, even helps in the preparation of polymers in a narrower particle size range and a lower bulk density range.

Through research, it is found that the temperature of the polymerization reaction is controlled at -20 to 100 ° C, and the purity of ethylene is controlled to be less than 5 ppm of carbon monoxide, less than 15 ppm of carbon dioxide, and less than 10 ppm of conjugated diene, so that particle size control can be achieved. At the same time, ultra-high molecular weight polyethylene is prepared. Preferably, the temperature of the polymerization reaction is 30-80°C, more preferably 50-80°C.

[Polyethylene Powder]

As mentioned above, the powder of the present invention is an ultra-high molecular weight polyethylene, the viscosity-average molecular weight (Mv) of the polyethylene is greater than 1×10 ⁶ , the polyethylene powder is spherical or quasi-spherical particles, and the average particle size is The diameter is 10μm-100μm, the standard deviation is 2μm-15μm, and the bulk density is 0.1g/mL-0.3g/mL. Preferably, the particle size distribution of the polyethylene powder is approximately normal distribution. The average particle size is preferably 20 μm-80 μm, more preferably 50 μm-80 μm. The standard deviation is preferably 5 μm to 15 μm, more preferably 6 μm to 12 μm, and still more preferably 8 μm to 10 μm. The bulk density is preferably 0.15 g/mL to 0.25 g/mL. The ultra-high molecular weight polyethylene with the particle size and bulk density is particularly suitable for graft modification. On the one hand, the modification space of polyethylene is greatly expanded; on the other hand, the processability of the polymer is significantly improved, It is suitable for the preparation of a wider range of articles; in this way, the application field of the polymer is effectively expanded.

At the same time, the polyethylene powder of the present invention also has the following excellent properties: firstly, the wear resistance is very excellent, which is several times higher than the wear resistance index of ordinary carbon steel and copper and other metals; secondly, due to the ultra-high molecular weight, the molecular The ultra-long chain makes the material high impact strength; thirdly, the chemical corrosion resistance of the polyethylene powder is stronger than that of general polyolefins; finally, the material has a wide temperature range, and it can be used at lower or higher temperatures. Can maintain good toughness and strength.

The embodiments of the present invention are described below through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through different specific embodiments, and various details in this specification can also be modified or changed based on applications in different aspects without departing from the spirit of the present invention.

Example 1

Ethylene homopolymer and its preparation

1) Preparation of catalyst

In the reactor fully replaced by high-purity nitrogen, 4.94g of anhydrous magnesium chloride, 18.9g of isooctyl alcohol, and 30ml of decane were sequentially added, and the temperature was raised to 130°C under stirring, and maintained for 2 hours, and then 2.65g of tetrabutyl titanate was added. The ester and 2.05g of diisobutyl phthalate were reacted at 130°C for another 1 hour, and finally cooled to room temperature to form a uniform and transparent solution, namely mixture I.

200ml of titanium tetrachloride was added to the reaction kettle, stirred and preheated to 0°C, and the mixture I was added dropwise to the titanium tetrachloride in about 2 hours. After the dropwise addition was completed, the temperature was started, and the temperature was increased to 110° C. within 2 hours. 1.23 g of diisobutyl phthalate, an internal electron donor, was added. After reacting at this temperature for 2 hours, the reaction liquid was removed, 200 ml of titanium tetrachloride was added again, and the reaction was performed for 2 hours. Finally, the reaction liquid was removed, and the remaining solid matter was washed with 60° C. hexane for 10 times, and dried to obtain the catalyst.

2) Slurry polymerization of ethylene:

Under the protection of high-purity nitrogen, the 1L autoclave was dried and deoxygenated, 150mL of n-hexane, 20mg of the above-mentioned catalyst and 12ml of triethylaluminum were sequentially added, and then ethylene gas was introduced to maintain 0.7MPa; wherein, in the ethylene, the carbon monoxide content less than 5 ppm, carbon dioxide less than 15 ppm, and conjugated diene content less than 10 ppm; at the beginning of the polymerization reaction, the system temperature was maintained at 80 ° C and the reaction time was 30 minutes. The obtained catalyst activity and polyethylene properties are shown in Table 1.

Example 2

Ethylene homopolymer and its preparation

The preparation method of the catalyst is the same as that in Example 1.

Slurry polymerization of ethylene:

Under the protection of high-purity nitrogen, the 1L autoclave was dried and deoxygenated, 150mL of n-hexane, 20mg of the above-mentioned catalyst and 12ml of triethylaluminum were sequentially added, and then ethylene gas was introduced to maintain 0.7MPa; wherein, in the ethylene, the carbon monoxide content less than 5ppm, carbon dioxide less than 15ppm, conjugated diene content less than 10ppm; the polymerization reaction started, the system temperature was maintained at 70 ° C, the reaction time was 30 minutes, the obtained catalyst activity and polyethylene properties are shown in Table 1.

Example 3

Ethylene homopolymer and its preparation

The preparation method of the catalyst is the same as that in Example 1.

Slurry polymerization of ethylene:

Under the protection of high-purity nitrogen, the 1L autoclave was dried and deoxygenated, 150mL of n-hexane, 20mg of the above-mentioned catalyst and 12ml of triethylaluminum were sequentially added, and then ethylene gas was introduced to maintain 0.7MPa; wherein, in the ethylene, the carbon monoxide content less than 5ppm, carbon dioxide less than 15ppm, conjugated diene content less than 10ppm; the polymerization reaction started, the system temperature was maintained at 50 ° C, the reaction time was 30 minutes, the obtained catalyst activity and polyethylene properties are shown in Table 1.

Figure 1 is a scanning electron microscope image of the polyolefin prepared in Example 3. It can be seen from Figure 1 that all the polyolefin particles exhibit good sphericity, spherical or quasi-spherical, and the particle size distribution is relatively uniform, with an average particle size. smaller.

Comparative Example 1

Ethylene homopolymer and its preparation

The preparation method of the catalyst is the same as that in Example 1.

Bulk polymerization of ethylene:

Under the protection of high-purity nitrogen, the 1L autoclave was dried and deoxygenated, 150mL of n-hexane, 20mg of the above-mentioned catalyst and 12ml of triethylaluminum were sequentially added, and then ethylene gas was introduced to maintain 0.7MPa; wherein, in the ethylene, the carbon monoxide content higher than 10 ppm, carbon dioxide higher than 20 ppm, and conjugated diene content higher than 20 ppm; at the beginning of the polymerization reaction, the system temperature was maintained at 110 ° C and the reaction time was 30 minutes. The obtained catalyst activity and polyethylene properties are shown in Table 1.

Table 1 The catalytic activity of the Ziegler-Natta catalyst prepared in the embodiment of the present invention and the properties of the prepared polyethylene

In the present invention, some other properties of the polyethylenes of Examples 1-3 and Comparative Example 1 were further tested, and it was found through testing that: (1) The abrasion resistance index of the polyethylenes of Examples 1-3 was higher than that of ordinary carbon steel or copper. The abrasion resistance index of Example 1 is several times higher; while the abrasion resistance index of Comparative Example 1 is slightly lower; (2) The impact strength of polyethylene in Examples 1-3 is greater than 10KJ/m ² , while the impact strength in Comparative Example 1 is higher than about 3KJ/m ² ; (3) the chemical corrosion resistance of the polyethylene powder in Examples 1-3 is stronger than that of general polyolefins, and the polyethylene powder in Comparative Example 1 is easily degraded under acidic conditions; (4) ) The polyethylene powder of Examples 1-3 has a wide range of use temperature, and can maintain good toughness and strength at lower temperature (eg, minus 30°C) or higher temperature (eg, 110°C).

Claims (11)

1. A method for preparing ultra-high molecular weight ultra-fine particle size polyethylene powder is characterized by comprising the following steps:

under the action of a catalyst, carrying out polymerization reaction on ethylene; wherein the temperature of the polymerization reaction is 50-80 ℃; in ethylene, the content of carbon monoxide is less than 5ppm, the content of carbon dioxide is less than 15ppm, and the content of conjugated diene is less than 10 ppm;

the catalyst is prepared by a method comprising the following steps:

(a) mixing magnesium halide and an alcohol compound in an organic solvent, heating and preserving heat, adding an auxiliary agent and part of internal electron donor, and reacting at a certain temperature to obtain a stable and uniform mixture I;

(b) adding the mixture I into a reactor, preheating to-30 ℃, and dropwise adding a titanium compound; or adding a titanium compound into a reactor, preheating to-30 ℃, and dropwise adding the mixture I;

(c) after the dropwise addition is finished, the reaction system is heated to 90-130 ℃ after 30 minutes-3 hours, and the rest internal electron donor is added for continuous reaction;

(d) filtering liquid in the reaction system, adding a titanium compound, and continuing the reaction;

(e) after the reaction is finished, post-treating to obtain the catalyst;

wherein the ethylene polymer produced has a viscosity average molecular weight (Mv) of greater than 1X 10⁶The ethylene polymer powder is spherical or spheroidal particles, the average particle size is 20-80 μm, the standard deviation is 2-15 μm, and the bulk density is 0.1-0.3 g/mL; the particle size distribution of the polyethylene powder is approximately normal.

2. The ultra-high molecular weight ultra-fine particle size polyethylene powder obtained by the preparation method of claim 1, wherein the viscosity average molecular weight (Mv) of said polyethylene is more than 1 x 10⁶The polyethylene powder is spherical or spheroidal particles, the average particle size is 20-80 μm, the standard deviation is 2-15 μm, and the bulk density is 0.1-0.3 g/mL; the particle size distribution of the polyethylene powder is approximately normal.

3. The powder of claim 2, wherein the polyethylene is an ethylene homopolymer.

4. The powder of claim 2, wherein the polyethylene has a viscosity average molecular weight (Mv) of 1.5 x 10 or more⁶(ii) a The polyethylene has a molecular weight distribution Mw/Mn of 2-15.

5. The powder of claim 4, wherein the polyethylene has a viscosity average molecular weight (Mv) of 1.5 x 10⁶～4.0×10⁶。

6. The powder according to claim 4 or 5, wherein the polyethylene has a molecular weight distribution Mw/Mn of 2 to 10.

7. The powder of claim 2, wherein the polyethylene powder has an average particle size of 50 μm to 80 μm.

8. The powder of claim 2, wherein the standard deviation is 5 μ ι η to 15 μ ι η.

9. The powder of claim 8, wherein the standard deviation is 6 μ ι η to 12 μ ι η.

10. The powder of claim 9, wherein the standard deviation is 8 μ ι η to 10 μ ι η.

11. The powder according to claim 2, wherein the bulk density of the powder is 0.15g/mL-0.25 g/mL.